View full sizeMary Altaffer / AP PhotoDemonstrators affiliated with the Occupy Wall Street movement assemble across the street from Zuccotti Park before marching through the streets of the financial district today in New York.

NEW YORK (AP) -- Police arrested protesters who sat on the ground and blocked traffic into New York's financial district on Thursday, part of a day of mass gatherings in response to efforts to break up Occupy Wall Street camps nationwide.

Police in riot helmets hauled several protesters to their feet and handcuffed them one block from Wall Street.

"All day, all week, shut down Wall Street!" the crowd chanted.

After several arrests, most of the protesters retreated down the street. A line of riot police followed them.

"You do not have a parade permit! You are blocking the street!" a police officer told protesters through a bullhorn.

The congestion brought taxis and delivery trucks to a halt.

The protest had been planned before the city and park owners cracked down on the encampment in Zuccotti Park, but took on added importance to the protesters after tents, tarps and sleeping bags were cleared out early Tuesday and the granite plaza across the street from the World Trade Center site was cleaned for the first time since the group arrived more than two months ago.

"This is a critical moment for the movement given what happened the other night," said Paul Knick, 44, a software engineer from Montclair, N.J. "It seems like there's a concerted effort to stop the movement and I'm here to make sure that doesn't happen."

The confrontations in New York followed early-morning arrests in Dallas, where police evicted dozens of protesters from their campsite near City Hall citing public safety and hygiene issues. They arrested 18 protesters who refused to leave.

Transit officials were preparing to deal with a crush of people as part of the protest billed as a national day of action. The group announced it would rally near the New York Stock Exchange, then fan out across Manhattan and head to subways, before gathering downtown and marching over the Brooklyn bridge.

Passer-by Gene Williams, a 57-year-old bond trader, joked that he was "one of the bad guys" but that he empathized with the demonstrators.

"They have a point in a lot of ways," he said. "The fact of the matter is, there is a schism between the rich and the poor and it's getting wider."

Similar protests were planned around the county.

New York City officials said they had not spoken to demonstrators but were aware of the plans.

"The protesters are calling for a massive event aimed at disrupting major parts of the city," Deputy Mayor Howard Wolfson said. "We will be prepared for that."